This invention relates to magazines for slide projectors, and particularly to magazines of the so-called "flexible" type in which a plurality of slides are held in individual clip-type holders for movement along an endless path having two elongated side sections joined by two arcuate end sections.
In such magazines, each slide is held with one edge adjacent the magazine body, which in the past has been a flexible belt, to extend outwardly therefrom, perpendicular to the side sections and radially of the arcuate end sections. One prior projector and magazine of this type are shown in U.S. Pat. No. 3,729,254. In the projector of this patent, the belt is mounted around two parallel shafts to give it the desired shape, one of the shafts being square in cross-section to hold the slides at ninety-degree angles to each other as they pass around this shaft, and being driven in ninety-degree steps to feed the slides through the projector and swing them one by one through a film gate or projection station adjacent the square shaft.
The advantages of flexible-magazine projectors now are well known, and include, among others, smooth and rapid slide changing, as fast as four or more per second, jam-free operation, and compact slide storage. Difficulties have been experienced, however, in the manufacture of the belt-type magazines, which typically utilize metal clips that are adhesively bonded to the outer side of a fabric belt, and in the adaptation of these magazines for slides having frames of different thicknesses. In addition, there is some question as to the long term durability of such magazines, and they generally lack a sophisticated appearance.
Consideration has been given to substitutes for such fabric-and-metal combinations, one alternative approach being shown in U.S. Pat. No. 3,820,886. In this patent, a number of different molded plastic holders are hingedly joined together, either by integral plastic hinges or by special hinged connections, thus eliminating the need for metal parts, and in at least some embodiments, simplifying the assembly operations required. Although the magazines of this patent are believed to be workable alternatives to the original belt-and-clip magazines, they have not found commercial acceptance, perhaps because of tooling costs involved in some embodiments, and perhaps because of assembly costs of others.
A prior flexible-belt projector, shown in U.S. Pat. No. 3,170,369, used a cartridge approach. In this magazine, the belt was mounted in an open-ended magazine box, on shafts that were permanently mounted in the magazine, one shaft being square, as in U.S. Pat. No. 3,729,254, to position the slides for projection. Bulk was an added disadvantage of this magazine, along with the same problems and questions that exist with the present magazines using unsupported belts and metal clips.
The principal objective of the present invention is to avoid the disadvantages of the magazines in the aforesaid patents, while maintaining the advantages of the flexible-type magazine, and specifically to provide a cartridge-type flexible magazine that is compact, both in construction and storage of slides, is capable of being mass-produced of molded plastic parts and economically assembled, and remains smooth, positive and trouble-free in operation, being virtually the same in this respect as the belt-type magazine.